Haaland shouldn't be sold if Dortmund really aim to win the Bundesliga title and achieve big things in the Champions League also. He is a critical player for them in terms of scoring many goals. I assume that he has scored most of Dortmund's goal only by himself since he came there. But as long as he has a this cheap release clause, it seems like impossible for Dortmund to keep him at the team anymore. This summer, I think that Dortmund won't be able to keep him and we will start watching him in another league.